Spark plug for internal combustion motors



Nov. 3, 1925. 1,560,081

C. A. LFFlTE/U ET AL SPARK PLUG FOR INTERNAL COMBUSTION MOTORS Filed May '7, 1924 INVENToR.

I I t a ATTORNEY.

Patented Nov.y 3, 1925'.

ITED SQ'F P A T EN T O F Fl C CHARLES A. kLAFFITnnun1vnftvILLrltM o# HENDRIX, or siw'nNiven, enen-GIA.

Application led- May 7,

Be it knownlthat. We, @inmunes A; LAFFI- 'rnau and `llV'rLnniM C. ilrlnnnni'x, citizens of the United States, residing at Savannah, in the count-y orv Chatham Yand` State oit Georgia, have invented .certain new .and useful Improvements in Spark lPlugs for Internal-Coinbustion Motors,y ot which the 'following is a specilication.

This inventionrelates to a ,spark plug for internal combustion motors, and i has forfits object to provide a plug of such class, in a manner as hereinafter set forth, with a, plu` rality of primary electrodes and a secondary electrode common to said primary electrodes to torni a plurality of independent ignition points or gaps and whereby each ot said priniar i electrodes can independently coact With'theseoondary electrode in a. manner so that it a primary electrode when coacting With'the secondary electrode becomes inactive, from soins cause, one oi"` the other priinary electrodes canlbe substituted there-tor to coact With the secondary electrode Without disconnecting the plug froi'nathe motor.

n further object` of' the invention' is to provide, in a manner ashereinal'ter set forth, a spark plug with means to permit ot substituting an uninipaired electrode'- carryingcore of insulation for a' damaged .core when occasion requires Without-.stopping the joperation ot `the motor. y

A further object offtheinventionis to pro-` vide, in a manner as'hereinafter set forth a spark' plug, having` means Vto' torni a Vseries or' independent v`spark gapsV and further with. means whereby the gapscan be Vindependently feinployed" for sparking' purposes or 'employed simultaneously.

Further objects of the" invention are to provide, in a inanner as hereinafter set forth, a spark plug, which is simple in 'its 'construction `and arrangement, strong, durable, compact, adjustable, AthoroughlyA efficient in its use, readily assembled, and comparatively inexpensive tomanuta'cture.

lith the foregoing and other-objectsin view, the inventionconsists ofthe novel construction, lcombination and arrangement of parts, as hereinaiterlniore' specificallyde-- scribed and illustrated? in the accompanying drawings, wherein is ,shownl an embodiment ofthe invention, butit is to be understood thatchanges, variations and `modilications can he resorted to'xwvhich 'cornefwithin 'ther scope ofthe claims hereunto appended.4

1924. SerialNo. 711,715.

tical section, showing theposition ot the is an elevation of'the core of inshell when substituting a nevvV core' vWithout I discontinuing Vthe operation ,ot the inotor.

Reterringto the drawings in detail, lfdenotes conventionallyl a' p'ort-ionvof the Wall ot. a cylinder of an internal coi'nbnstion engine 'and to" which isadaptedto be detachably connected -the spark plug. The AWall l has yan!'opening2 'Withfthe Wall thereoi' threaded. l

.A spark plug in accordance vvith thisA inventionconiprises a metallic shell-formed ofV an outer- `portion 3' and an inner` portion 4 and"y with" the' 'Oriner ofl greater diameter than'the latter. The inner portion 4 isinset v,with respect to fthe outer `porti-on. 8,

whereby shoulders and Gare -toi-ined. "The" innerportion 4' is peripherally threaded,` as at Q1/and interiorly threadedljat its inner end,.'as "at 8. -The length otthe inner.' portion 4 is such thatfWhen theshellis mounted inv position, 'the said'tinneri'portion 4 will extend asubstantial distance 'Within 'the cylinder oftheengine `Vhenfthe shell is connected to the cylinder, theinner portion 4, extends". through the opening 2 .and the threads ot' vsaidj portion 4 engage With 4the threads lon the Wall ofthe opening 2 and further when the shell isinountedin position the shoulder 6 abuts `against vthe outer tace of the vWall l.

' The inner end" of .the portion 4 ot the rshell is closed by aperipherallyfthreaded disly 9 Whichengages with the internal threads 8` otlthe portion 4. The disk 9 is grooved, as at l0, to facilitate the positioningthereof, and'said diskjl is ot substantial thickness but ot suchthiclniess as not to close :entirely thatpart foi the innerportion 4 ivhichpro- `iects inwardly from the inner face of the wall 1.

The inner end of the portion 4 of the shell is provided with a pair of diametrically opposed openings 11 of substantial diameter and said openings 11 are arranged in the portion 4 of the shell, outwardly with respect to the disk 9 when the latter is secured in the inner end of the shell. Preferably the length of the inner portion 4 of the shell is such that when the shell is mounted in position, it will extend a suicient distance into the motor cylinder so that the openings 11 will be arranged between the disk 9 and the inner face of the wall 1, or in other words the diameter of each of the openings 11 is such whereby the openings will be positioned to extend from the disk 9 to the inner face of the wall 1, as clearly shown in Figure 2. The openings 11 allow for the entrance of the compressed charge into the shell outwardly with respect to the 4disk 9 to provide for the ignition of the charge. The purpose of the disk 9 will be hereinafter referred to.

The inner face of the outer portion 3 of the shell, at its outer end, is threaded, as at 12, for a purpose to be presently referred to. Seated against the shoulder is a metallic washer 13, having its top edge formed with a lug 14. The shoulder 5 is bevelled as well asthe lower or inner edge of the washer 13. The threads on the inner face of the outer portion 3 of the shell are engaged by a peripherally threaded anged packing gland 15 which abuts against a packing element 16 arranged within the outer portion 3 of the shell.

Arranged within the shell and extending through and projecting outwardly with respect to the gland 15 is a core of insulation and which is formed of an outer cylindrical portion 17, an inner cylindrical portion 18 of the same diameter as the portion 17, and an intermediate portion 19 of greater diameter than either of the portions 17, 18. The outer edge of the intermediate portion 19 is bevelled, as at 20, and the inner edge 21 of said portion 19 is plane and provided with a recess 22 and into which extends the lug 14 of the washer 13. When the core is mounted in position, it is surrounded by the washer 13 and the latter abuts against the edge 21 of the intermediate portion 19 and with the lug of the washer 13 extending into the recess 22. See Figure 5. The setting up of the washer 13 with respect to the intermediate portion 19, in the manner as stated, prevents the washer 13 from shifting circumferentially with respect to the inner portion 18 of the core.

The inner terminus of the inner portion 18 of the core, is convex in cross section, as indicated at 23, and said inner terminus is provided with a series of pockets which merge into each other at the inner ends thereof, and the number of the pockets depends on the number of primary electrodes employed, andas the plug is shown as provided with four primary electrodes, four pockets are formed in the inner terminus of the inner portion 18, and said pockets are radially disposed. The pockets, at the inner terminus of the inner portion 18 of the core,are indicated at 24, 25, 26 and 27, and the top wall of each of said pockets conforms in curvature to the convex curvature of the inner terminus of the inner portion 18. The pockets merge into each other at the axis of the core at the inner ter minus of the inner portion 18. When the number of primary electrodes is increased, the number of pockets will be correspondingly increased, and the same arrangement is had when the number of primary electrodes is decreased. rllhe length of each of the pockets is materially greater than the width 'thereof and the outer end wall of each of said pockets is semi-circular, as at 28.

The outer portion 17 of the core at a point a substantial distance from the outer end thereof, has its periphery provided with a series of spaced concavities and the number of said concavities will correspond to the number of primary electrodes, and as shown the said outer portion 17 of the core is formed with four concavities indicated at 29, 30, 31 and 32.

The intermediate portion 19 of the core is mounted in the outer portion 3 of the shell, and is seated against the washer 13 and has bearing thereagainst the packing element 16. See Figure 2. The gland 15 when secured to the outer portion 3 of the shell, clamps the core in position. The di ameter of the portions 17 and 18 of the core is such as to provide for said portions to snugly engage respectively the gland 15 and the inner portion 4 Yof the shell. The diameter of the intermediate portion 19 of the core is such as to snugly engage the inner face of the outer portion 3 of the shell.

Embedded within the core is a plurality of primary electrodes, as shown four in number, and which are indicated by the reference characters 33, 34, 35 and 36. The primary electrodes are positioned between the axis and the periphery of the core and are arranged equi-distant with respect to each other. Each of the primary electrodes has an angle-shaped upper terminal 37 which projects` outwardly and an angleshaped inner terminal 38, which projects inwardly. Each of the primary electrodes extends from a concavity to a. pocket or in yother words, the electrode extends from the concavity 29 to the pocket 24, the electrode 34 from the concavity 30 to the pocket 25, the electrode from the concavity 31 to the pocket 26 and the electrode 36 from-the concavity 32 to the pocket 27. Each of the electrodes has its inner terminal portion 38 snugly engaging the upper wall of its respective pocket, and each of said electrodes when entering its .respective pocket is spaced from the end wall 28 of the pocket. The free ends of the inner terminal' portions of the electrodes are positioned a substantial distance from the inner ends of the pockets. See Figure 6.

The upper terminal portions 37 of the electrodes extend into the concavities a sui:- licient distance. See Figure 3.

Embedded within the core is an angleshaped secondary electrode, which is common to said primary electrodes and said secondary electrode comprises a leg 39 positioned Aaxially of the core and a leg 40 disposed at right angles with respect to the anis or the core. The leg 39 is of a length slightly less than the length of the inner portion 13 of the core, and the lower end of said leg 39 projects int-o the pockets at the points or' mergence thereof, and the said inner end of the leg 39, which is indicated at 41, associates with the inner terminal portions 38 'of the primary electrodes. The end 4l is positioned a substantial distance from each of said inner terminals 38 and provides in connection therewith a spark gap. The leg 40 projects outwardly from the inner portion 13 of the core and extends into the washer 13, as indicated at 42. See Figure 4. The leg` 40 has electrical contact with the Washer 13 and said leg 40 is arrangedbetween a pair of primary electrodes. See Figure 4.

Shiftably mounted upon the outer end of the portion 17 of the core is a cap member 43 of insulation and which is provided with a socket 44 for the reception of the upper portion ott the core and which extends into the socket 44 a sufficient distance so that the cap member will inclose the concavities formed in the core. See Figure 2. The cap member 43 is what may be termed a circuit opening and closing element and is provided with a plurality of binding posts, and the number of said posts corresponds to the number of primary electrodes and as shown the cap member 43 has connected therewith four binding posts, indicated at 45, 46, 47 and 48, and when the primary electrodes are to be independently used, but one circuit wire is employed, as indicated at 49, and which by way of example is attached to the binding post 47, but if the primary electrodes are to be simultaneously employed, then to each of the binding posts a circuit wire would be attached. Carried by each of the binding posts, as well as depending therefrom, is a resilient conductor 50, having its lower end offset, as at 51, and fixed to said offset lower end is a contact 52 which is slidably mounted in the walls of the pockets,

cap member 43 and extends into a concavity for engagement with the angle-shaped upperterminus 37 of a primaryelectrode for the purpose of electrically connecting said electrode with the circuit conductor 49.

`The 4resilient conductors 50, in connection withfthe contacts 52, act as means for connecting the cap member 43 with the core, due yto the ffact that the resilient conductors 50 normally maintain the contacts 52 in the concavities, but the engagement-is such as' not to prevent shifting oi' the cap member 43 upon the core, when `occasion requires.

The construction and arrangement of the plug issuch, that the primary electrodes can be thrown independently in active position. As shown in Figure 2, the primary electrode 35 is inactive positiondue tothe fact that it is electrically connected with the circuit, connection 49. Now, if theprimaryelectrode should become impaired or damaged, the cap member 43 can be shiftechso that the circuit wire 49- can be electrically-connected 'to any one oi' the primary electrodes, byway of example, the primary electrode 36, and this connection is had as the carp member 43 will be shifted so that the resilient conductor 50, carried by the binding post 47 will be moved to a position whereby the contact 52 carried thereby will engage in the concavity 42 and electrically connect With'the upper terminal portion37 of the primary electrode 36. The foregoing operation Vis carried out until all ofthe primary electrodes have become `activeand it :all of said primary electrodes become impairedl ordainaged, `then the core is removed and .la newv one with the primary and secondary electlrollesv substituted and connected to the s 1e IVhen it is desired to substitute a new core, the shell is shifted outwardly with respect to the wall l, until-the openings 11 are closed by the wall of the opening 2, and owing to the fact that the inner end of the portion4 of the shell is closed by the disk 9, the cylinder will be blocked olif without discontinuing the operation of the motor.

The damaged core is then removed and a new one substituted and after the latter has been secured in position the shell is then shifted to the position shown in vFigure 2. If the inner end of the shell-was not provided with the disk 9, the substitution of a new core could not be had without discontinuing the operation of the motor.

The providing the inner terminus of the core of convex curvature, as well as the top overcomes short circuiting, due to clogging up oi' the spark gaps or the fouling of the inner ends of the electrodes by an accumulation oi' oil. The curvature at the inner end of the core causes the oil or constituents of the charge to flow away from the 'inner termini of the electrodes, then any accumulation upon the plug 9 would be vaporized.

The plug construction is such that it provides for a pluralityof independent sparl ing points so that if one point becomes dead, another point can be switched in and under such conditions it provides for a single plug having means whereby it' will equal the employment ot a plurality of plugs each formed with a. single spark gap o-r firing point, as a plug in accordance with this invention, having by Way of example four firing points or spark gaps will take the place of tour plugs each provided with a single liring point or spark gap, therefore reducing materially the cost of maintenance.

It is thought that the many advantages of a spark plug, in accordance With this invention, can be readily understood, and although the preferred embodiment of the invention is as illustrated and described, yet changes in the details ot' construction can be had which Will fall Within the limits of the invention as claimed.

IVhat We claim is I. A spark plug comprising a shell, a core mounted therein and provide-d at its inner end with a plurality of pockets, asecondary electrode carried by the core and having its inner end arranged axially with respect to said pockets and its upper end projecting laterally from the core, a plurality of primary electrodes mounted in the core and having their innerends extended in said pockets and spaced from the inner end of said secondary electrode, said secondary electrode common to said primary electrodes, and shit-table means carried by the core and adapted to selectively engage with said primary electrodes to cause the selected primary electrode to coact With the secondary electrode for ignition.

2. A spark plug comprising a core adapted to be connected to the cylinder and provided With a plurality of primary electrodes having exposed inner ends and further provided With a secondary electrode having an exposed inner end common to the exposed inner ends of the primiary electrodes, said secondary electrode having its outer end projecting 'from said core, said primary electrodes having their outer ends arranged Within said core and exposed, and a shittable cap member mounted on said core and provided with spring controlled circuit opening and closing means selectively engaging With the exposed ends of said primary electrodes to cause the selected primary electrode to independently coact with the secondary electrode for ignition.

S. A spark plug comprising an electrode carrying core having its inner end of convex curvature and provided with a plurality of pockets having the top Walls thereof corresponding in curvature to the curvature of said inner end, the curvature of said inner end and walls of the pockets overcoming short circuiting.

In testimony whereof, we aiiix our signatures hereto.

CHARLES A. LAFFITEAU. WILLIAM C. HENDRIX. 

